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further WIP on the ActivityImplPtr feature. Now it compiles (but fails)
[simgrid.git] / src / simix / ActorImpl.hpp
index f2a18a6..9b49949 100644 (file)
@@ -9,12 +9,13 @@
 #include "simgrid/s4u/Actor.hpp"
 #include "src/simix/popping_private.h"
 #include "xbt/swag.h"
-#include<list>
+#include <list>
 
 typedef struct s_smx_process_exit_fun {
   int_f_pvoid_pvoid_t fun;
   void *arg;
-} s_smx_process_exit_fun_t, *smx_process_exit_fun_t;
+} s_smx_process_exit_fun_t;
+typedef s_smx_process_exit_fun_t* smx_process_exit_fun_t;
 
 namespace simgrid {
 namespace simix {
@@ -69,16 +70,23 @@ public:
 
   /* Refcounting */
 private:
-  std::atomic_int_fast32_t refcount_{1};
+  std::atomic_int_fast32_t refcount_{0};
+
 public:
   friend void intrusive_ptr_add_ref(ActorImpl* process)
   {
-    process->refcount_.fetch_add(1, std::memory_order_relaxed);
+    // std::memory_order_relaxed ought to be enough here instead of std::memory_order_seq_cst
+    // But then, we have a threading issue when an actor commits a suicide:
+    //  it seems that in this case, the worker thread kills the last occurrence of the actor
+    //  while usually, the maestro does so. FIXME: we should change how actors suicide
+    process->refcount_.fetch_add(1, std::memory_order_seq_cst);
   }
   friend void intrusive_ptr_release(ActorImpl* process)
   {
     // inspired from http://www.boost.org/doc/libs/1_55_0/doc/html/atomic/usage_examples.html
     if (process->refcount_.fetch_sub(1, std::memory_order_release) == 1) {
+      // Make sure that any changes done on other threads before their acquire are committed before our delete
+      // http://stackoverflow.com/questions/27751025/why-is-an-acquire-barrier-needed-before-deleting-the-data-in-an-atomically-refer
       std::atomic_thread_fence(std::memory_order_acquire);
       delete process;
     }